Olly Murs is getting fit with the help of the personal trainer who got David Walliams into shape before he swam the Channel.
The Sun reported that the Troublemaker singer, 29, is undergoing a strict training programme under the eye of Professor Greg Whyte, a two-time Olympian.
After a workout in Harley Street, central London, the singer tweeted: "You completely demolished me this morning!!
"Yes I feel sick, yes I can't move BUT yes can't wait for more cardio!" he wrote.
Greg, a professor of sport and exercise science, celebrity trainer and "ultra-endurance nutter" is well known for his Comic Relief projects.
He helped Cheryl Cole, Chris Moyles and Gary Barlow to climb Mount Kilimanjaro and Eddie Izzard to run 43 Marathons in 51 days.
He is also helping Davina McCall, who calls him her Obi-Wan Kenobi, prepare for the Davina Beyond Breaking Point BT Sport Relief Challenge next month.
The former Big Brother presenter is cycling, swimming through lakes, fell running and mountain hiking and taking part in a final marathon to travel 500 miles from Edinburgh to London.